﻿//
// ReadOnlyCollection.cs
//
// Author:
//   Leszek Ciesielski (skolima@gmail.com)
//
// (C) 2011 Leszek Ciesielski
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Sandcastle.Construction.Internal
{
    internal sealed class ReadOnlyCollection<T> : ICollection<T>
    {
        IEnumerable<T> backingEnumerable;

        public ReadOnlyCollection(IEnumerable<T> enumerable)
        {
            backingEnumerable = enumerable;
        }

        public void Add(T item)
        {
            throw new InvalidOperationException("This collection is read-only.");
        }

        public void Clear()
        {
            throw new InvalidOperationException("This collection is read-only.");
        }

        public bool Contains(T item)
        {
            List<T> backingList = backingEnumerable as List<T>;
            if (backingList != null)
                return backingList.Contains(item);
            return backingEnumerable.Contains(item);
        }

        public void CopyTo(T[] array, int arrayIndex)
        {
            List<T> backingList = backingEnumerable as List<T>;
            if (backingList != null)
            {
                backingList.CopyTo(array, arrayIndex);
                return;
            }
            int i = arrayIndex;
            foreach (var item in backingEnumerable)
            {
                array[i++] = item;
            }
        }

        public int Count
        {
            get
            {
                var backingList = backingEnumerable as List<T>;
                if (backingList == null)
                    backingEnumerable = backingList = new List<T>(backingEnumerable);
                return backingList.Count;
            }
        }

        public bool IsReadOnly
        {
            get { return true; }
        }

        public bool Remove(T item)
        {
            throw new InvalidOperationException("This collection is read-only.");
        }

        public IEnumerator<T> GetEnumerator()
        {
            return backingEnumerable.GetEnumerator();
        }

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return backingEnumerable.GetEnumerator();
        }
    }
}
